Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

An ultrasonic transducer for use in a fluid medium includes at least one
transducer core having at least one electroacoustic transducer element,
and further includes at least one housing having at least two housing
parts. At least one first housing part at least partially encloses the
transducer core such that a rear side of the electroacoustic transducer
element which faces away from the fluid medium is accessible.
Furthermore, at least one second housing part is connected to the first
housing part. The ultrasonic transducer is essentially terminated by the
second housing part on its side, which faces away from the fluid medium.

Claims:

1-12. (canceled)

13. An ultrasonic transducer for use in a fluid medium, comprising: at
least one transducer core including at least one electroacoustic
transducer element; and at least one housing having at least two housing
parts, wherein at least one first housing part at least partially
encloses the transducer core such that a rear side of the electroacoustic
transducer element which faces away from the fluid medium is accessible,
and wherein at least one second housing part is connected to the first
housing part and terminates the ultrasonic transducer on a side which
faces away from the fluid medium.

14. The ultrasonic transducer as recited in claim 13, wherein the first
housing part surrounds the transducer core in a ring-shaped manner.

15. The ultrasonic transducer as recited in claim 14, wherein the
electroacoustic transducer element is one of (i) aligned flush with the
first housing part or (ii) protrudes beyond the first housing part on the
side which faces away from the fluid medium.

16. The ultrasonic transducer as recited in claim 14, wherein the second
housing part is pot-shaped element and is put over the first housing part
from the side which faces away from the fluid medium.

17. The ultrasonic transducer as recited in claim 14, wherein the first
housing part and the second housing part are connected to one another by
welding.

18. The ultrasonic transducer as recited in claim 14, further comprising:
at least one contact bridge electrically contacting the electroacoustic
transducer element, wherein the contact bridge protrudes through the
second housing part into an inner chamber of the ultrasonic transducer
and is electrically connected to the electroacoustic transducer element
in the inner chamber.

19. The ultrasonic transducer as recited in claim 18, wherein the contact
bridge is connected to the first housing part by at least one of a
form-locked and a force-fitted connection.

20. The ultrasonic transducer as recited in claim 18, wherein the contact
bridge at least partially encloses the electroacoustic transducer element
and provides an electromagnetic shield.

21. The ultrasonic transducer as recited in claim 20, wherein the first
housing part and the second housing part are plastic material.

22. A method for manufacturing an ultrasonic transducer for use in a
fluid medium, comprising: producing a transducer core including at least
one electroacoustic transducer element; providing at least one first
housing part which at least partially encloses the transducer core such
that a rear side of the electroacoustic transducer element which faces
away from the fluid medium is accessible; providing at least one second
housing part; and connecting the first housing part and the second
housing part in such a way that the ultrasonic transducer is terminated
by the second housing part on a side which faces away from the fluid
medium.

23. The method as recited in claim 22, wherein the first housing part and
at least an adjusting body element of the transducer core are applied
onto a sealing film, and wherein an intermediate space between the at
least the adjusting body element of the transducer core and the first
housing part is at least partially filled by at least one of a damping
material and a decoupling material.

24. The method as recited in claim 22, wherein before the connection of
the first housing part and the second housing part, a contact bridge for
contacting the electroacoustic transducer element is connected to the
first housing part by at least one of a form-locked and a force-fitted
connection.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an ultrasonic transducer for use
in a fluid medium.

[0003] 2. Description of Related Art

[0004] Ultrasonic transducers are known in various fields of use from the
related art. For example, ultrasonic transducers are used in automotive
engineering in ultrasonic flow meters, for example, in the exhaust system
and/or in the intake system of internal combustion engines. Examples of
such ultrasonic transducers are described in published German patent
application document DE 10 2007 037 088 A1 or German Patent Application
DE 10 2008 055 126.0 of the applicant (which is not believed to be prior
art). Ultrasonic flow meters are based in many cases on two ultrasonic
transducers, which are situated offset in a flow tube in the flow
direction and mutually send one another ultrasonic signals. Measuring
systems may also be used in which at least one reflector is provided, for
example, in the form of plug-in sensors. Further applications of
ultrasonic transducers are, for example, filling-level meters or distance
meters, for example, in so-called Park Pilot systems.

[0005] In many cases, ultrasonic transducers have an electroacoustic
transducer element in the form of a piezoceramic. In order to achieve an
impedance adjustment, i.e., in particular a reduction of reflection
losses at the interface between the ultrasonic transducer and the fluid
medium in which the ultrasonic transducer is to be used, in many cases
so-called adjusting bodies are used, which ensure at least partial
impedance compensation between the piezoceramic and the impedance of the
fluid medium. For example, ultrasonic transducers based on a piezoceramic
in conjunction with so-called λ/4 impedance adjustment layers are
known. Examples of such adjusting bodies, which may also be used in the
scope of the present invention, are described in published German patent
application document DE 10 2007 037 088 A1 or German patent application
DE 10 2008 055 126.0.

[0006] Furthermore, ultrasonic transducers having a housing in the form of
a one-piece sleeve and a ring-shaped rear cover are known from the
related art. Such ultrasonic transducers are used, for example, in Park
Pilot systems. In this case, the piezoceramic is typically first
electrically contacted in that, for example, wires are welded to the
piezoceramic and to the contact pin connected to the cover ring.
Subsequently, the piezoceramic is then typically held with the aid of a
vacuum pad gripper through the cover ring and inserted into the sleeve
jointly with the cover ring and the connecting wires. During this
procedure, the connecting wires receive the bending shape which is
desired inside the later ultrasonic transducer for the purpose of ideal
durability. Before the vacuum pad gripper may be removed, an adhesive
must typically be activated between the piezo and the sleeve, which
occurs in many cases in the form of ultraviolet radiation, which is
typically also introduced through the cover ring.

[0007] In practice, this type of assembly is, however, associated with
various technical requirements and disadvantages in practice. Thus,
one-piece transducer sleeves must typically be implemented as very deep,
because an interior of the transducer sleeves must be filled up with a
specific quantity of damping material. Furthermore, this depth of the
transducer sleeve is typically required to allow fastening of contact
pins or re-contacting in order to ensure an appropriate guide length for
a precisely aligned installation, for example, in a plug-in sensor
housing, or to make the general handling of the entire transducer easier.
However, the handling during the construction process is typically made
more difficult by this depth of the transducer sleeve, because the
piezoelement must be sunk deep into the transducer sleeve. Electrical
contacting of the piezoceramic which is suitable for mass production is
then only possible with difficulty inside the sleeve. In contrast, if the
electrical contacting of the piezoceramic is performed before the joining
with the optional adjusting body, the piezoceramic, the connecting wires,
the contact pins, and optionally the transducer cover or transducer cover
ring must remain fixed or positioned relative to one another in the scope
of the joining procedure. Such a method is extraordinarily complex.

BRIEF SUMMARY OF THE INVENTION

[0008] Therefore, an ultrasonic transducer for use in a fluid medium and a
method for manufacturing an ultrasonic transducer for use in a fluid
medium are proposed, which at least partially avoid the disadvantages of
known ultrasonic transducers and manufacturing methods. The ultrasonic
transducer may in particular be manufactured as per a method according to
the present invention, and the method may in particular be used to
manufacture an ultrasonic transducer according to the present invention.
Reference may accordingly be made to the description of the ultrasonic
transducer for possible embodiments of the method and vice versa.

[0009] The present ultrasonic transducer includes at least one transducer
core having at least one electroacoustic transducer element. An
electroacoustic transducer element is to be understood as a fundamentally
arbitrary element which may convert electrical signals into acoustic
signals and vice versa. In particular, this may be a monolithic element.
The electroacoustic transducer element preferably includes a
piezoelectric transducer element or is implemented as a piezoelectric
transducer element. Accordingly, in the scope of the present invention,
without restriction of other possible embodiments of the electroacoustic
transducer element, the terms "piezo," "piezoceramic," and "piezoelectric
transducer element" are also used as synonyms for the term
"electroacoustic transducer element." In addition, the transducer core
may include other elements as explained in greater detail below. For
example, the transducer core may include at least one adjusting body on a
side which faces toward the fluid medium, for example, according to the
above-described related art. This adjusting body is configured to improve
an acoustic coupling between the electroacoustic transducer element and
the fluid medium, for example, air or a liquid. Ideally, the adjusting
body provides a material whose impedance is the geometric mean value of
the impedances of the electroacoustic transducer element and the fluid
medium. In the real ultrasonic transducer and in particular in the case
of a gaseous fluid medium, an adjusting body having a different,
typically higher acoustic impedance will typically be used. The adjusting
body may also include multiple materials having different acoustic
impedances and/or a material having an acoustic impedance gradient. For
example, the transducer core may have an emission surface, which faces
toward the fluid medium and via which ultrasonic signals may be delivered
to the fluid medium and/or ultrasonic signals may be absorbed from the
fluid medium. The emission surface may be situated, for example, in an
opening of a housing, which will be explained in greater detail below.
For example, this opening may be surrounded by an edge of the housing,
for example, in a ring-shaped manner. Other geometries are also
conceivable. The emission surface may be aligned flush with the edge of
the housing or may also be situated in another plane, for example,
slightly offset into the interior of the housing or slightly offset in
relation to the edge toward the fluid medium.

[0010] Furthermore, the ultrasonic transducer includes at least one
housing. This housing may be implemented as sleeve-shaped in particular.
A housing is understood as an element which terminates the ultrasonic
transducer essentially at the outside and gives the ultrasonic transducer
its essential shape at the outside. The housing, as explained in greater
detail below, may in particular be manufactured from a metallic material
and/or a plastic material and may protect the ultrasonic transducer
against external mechanical and/or chemical influences and/or against
temperature and/or pressure influences.

[0011] One idea of the present invention is that the assembly and the
construction of the ultrasonic transducer may be simplified significantly
if the housing is implemented in at least two parts. Correspondingly, the
housing has at least two housing parts. These housing parts are
preferably implemented completely separately and accordingly may
preferably be manufactured and/or handled completely independently of one
another.

[0012] At least one first housing part is provided, which at least
partially encloses the transducer core. For example, the housing part may
entirely or partially enclose an adjusting body of the transducer core
and/or the electroacoustic transducer element. The first housing part may
accordingly be implemented, for example, as ring-shaped or tubular, for
example, having a round or polygonal cross section. An internal diameter
of this housing part may precisely match the external diameter of the
transducer core, or an intermediate space may be provided between the
housing part and the transducer core, as explained in greater detail
below.

[0013] The first housing part encloses the transducer core in such a way
that a rear side of the electroacoustic transducer element, which faces
away from the fluid medium, is accessible. The term accessible is to be
understood in the scope of the present invention as a configuration in
which the first housing part has at least one opening on the rear side,
for example, an opening having a greater opening width than the
transducer core, through which the rear side of the electroacoustic
transducer element may be accessed, for example, for contacting the
electroacoustic transducer element. The opening and/or the transducer
element may be implemented in particular in such a way that the
transducer core may be introduced through the opening in the first
housing part into the first housing part and/or removed therefrom. For
example, this rear side of the electroacoustic transducer element may be
aligned flush with the rear side of the first housing part or even
protrude beyond this first housing part, so that it is accessible for
electrical contacting, for example. Alternatively, the first housing part
may also protrude slightly on the rear side, so that the rear side of the
electroacoustic transducer element is slightly offset into the interior
of the housing in relation to the rear side of the first housing part,
the rear side of the electroacoustic transducer element still being
accessible for electrical contacting, however.

[0014] Furthermore, at least one second housing part is provided, which is
connected to the first housing part, for example, via an integral and/or
force-fitted and/or form-locked connection. This second housing part is
implemented and situated in such a way that it essentially terminates the
ultrasonic transducer on its side, which faces away from the fluid
medium.

[0015] However, here, a termination does not mean a hermetic termination,
but rather a definition of the outer form of the ultrasonic transducer on
the side, which faces away from the fluid medium and/or a mechanical
stabilization of components of the ultrasonic transducer accommodated in
the housing. Furthermore, at least partial protection from external
influences may be ensured. "Essentially" in this regard may be understood
as a termination in which at least small openings, for example, for
feedthroughs or as a compensation opening with respect to thermal
expansion of parts of the transducer (e.g., a damping element), may also
be tolerated. "Essentially terminated" may therefore be understood in
particular as an embodiment of the second housing part on the side, which
faces away from the fluid medium in which the transducer interior, for
example, the electroacoustic transducer element and/or the entire
transducer core and/or a decoupling element and/or a damping element, may
be held in the interior of the housing by the second housing part, so
that these components may not be removed from the housing. In particular,
the second housing part may provide a rear-side support, on which one or
multiple of the elements transducer core, electroacoustic transducer
element, decoupling element, damping element, damping and/or decoupling
material, or also other elements which are situated in the interior of
the housing may be supported. Thus, for example, the second housing part
may include at least one supporting element on its side, which faces away
from the fluid medium, for example, an inwardly protruding collar, on
which one or multiple of the mentioned elements of the housing interior
may be supported, so that, for example, a pressure of the fluid medium
may be absorbed. For example, it may be ensured in this way that a
sealing film on the side of the ultrasonic transducer, which faces toward
the fluid medium, is pressed inward as little as possible in the event of
a compression load. If at least one rear-side opening is provided in the
second housing part, it is also not to be selected as excessively small,
however, since the supporting effect is always improved in this case, but
thermally induced expansions of the transducer interior, for example of a
damping molding compound, would load the optional sealing film all the
more. Depending on the hardness, coefficient of thermal expansion, and
filling volume, an appropriate compromise for the ideal opening size of
the second housing part may be found in practice.

[0016] As described above, the first housing part may surround the
transducer core in a ring-shaped manner in particular. The first housing
part may accordingly be implemented entirely or partially as a ring
and/or as a ring-shaped sleeve. For example, the first housing part may
have a front surface, in particular a circular front surface, which faces
toward the fluid medium. An emission surface of the transducer core,
i.e., a surface via which acoustic signals may be delivered from the
transducer core to the fluid medium and/or via which acoustic signals may
be absorbed from the fluid medium by the transducer core, may be
surrounded by this front surface in a ring-shaped manner. For example,
the emission surface may be situated in one plane together with this
front surface of the first housing part. Such an embodiment is
particularly preferred if, as explained in greater detail below, at least
one sealing film is provided, which shields and/or seals a housing
interior of the ultrasonic transducer against influences from the fluid
medium, for example, chemical influences and/or pressure influences. Such
a sealing film may be glued or connected in another way, for example, to
the front surface of the first housing part and/or to the emission
surface.

[0017] The electroacoustic transducer element may in particular be aligned
flush with the first housing part or protrude beyond the first housing
part on the side, which faces away from the fluid medium. This embodiment
is particularly advantageous to ensure simple electrical contacting of
the electroacoustic transducer element.

[0018] The second housing part may be implemented in particular in the
form of a pot. In this case, the second housing part, for example, may be
put over the first housing part from the side, which faces away from the
fluid medium. The first housing part and the second housing part may be
connected to one another with the aid of an integral connection process,
for example, in particular a welding process. In particular in the case
of plastic materials, but also in the case of other materials, ultrasonic
welding is recommended in particular. Alternatively or additionally,
however, other connection technologies may also be used, for example,
force-fitting and/or form-locking and/or integral connection
technologies, for example, by laser welding, gluing, or by clipping the
second housing part onto the first housing part or vice versa.

[0019] Furthermore, the ultrasonic transducer may include at least one
contact bridge for electrically contacting the electroacoustic transducer
element. For example, the contact bridge may include one, two, or more
electrical contacts for contacting electrodes of the electroacoustic
transducer element. The at least one contact bridge may be implemented as
essentially dimensionally stable, for example, i.e., in such a way that
it does not deform or only deforms insignificantly at least under the
influence of its intrinsic weight force. The contact bridge may be
manufactured from a metallic material in particular. The contact bridge
may protrude through the second housing part into an inner chamber of the
ultrasonic transducer and may be electrically connected therein to the
electroacoustic transducer element. This electrical connection between
contact bridge and electroacoustic transducer element may be performed,
for example, by directly contacting the electroacoustic transducer
element via the contact bridge. Alternatively or additionally, however,
other connection technologies may also be used, for example, wire bond
technologies. Such bonding technologies may be technically implemented in
a particularly simple way, since an access to the electroacoustic
transducer element is made easier by the two-part or multipart embodiment
of the housing. The contact bridge may be connected to the first housing
part in particular. The contact bridge may be spatially fixed in this way
in particular. This connection may include a form-locked and/or
force-fitted connection, for example. For example, the contact bridge may
include one or multiple connection elements, for example clips, with the
aid of which it is possible to plug and/or clip the contact bridge onto
the first housing part.

[0020] The contact bridge may fulfill other tasks in addition to
electrical contacting of the electroacoustic transducer element. Thus,
for example, it may be implemented at least partially as an
electromagnetic shield, for example. The contact bridge may accordingly
at least partially enclose the electroacoustic transducer element, for
example.

[0021] As explained above, the transducer core may include additional
elements in the at least one electroacoustic transducer element. For
example, the transducer core may include at least one adjusting body, for
example, according to the above-described related art. This adjusting
body may improve an acoustic coupling between the electroacoustic
transducer element and the fluid medium. The first housing part may at
least partially surround the adjusting body, for example, enclose it in a
ring-shaped manner.

[0022] The first housing part and the second housing part may be
manufactured, as described above, entirely or partially from a metallic
material and/or a plastic material and/or from other materials. Materials
which have good intrinsic damping and simultaneously the possibility for
also manufacturing filigree structures are particularly preferred. Thus,
for example, liquid crystal polymers (LCP) may be used. Alternatively or
additionally, other plastics may also be used, for example, PPA
(polyphtalamide), PBT (polybutylene terephthalate), and/or PEEK
(polyether ether ketone), and/or other plastics. These plastic materials
may be implemented as unfilled or also filled, for example, having a
filling made of glass fibers, ceramic, carbon, or similar materials.

[0023] The first housing part may have an opening, which faces toward the
fluid medium in particular. For example, the first housing part, as
described above, may have a front surface, for example, a ring-shaped
front surface, which encircles the opening. The emission surface of the
transducer core may be situated inside this opening. The opening may be
closed off by at least one sealing film. The sealing film may be
connected, for example, to the first housing part, the front surface, for
example.

[0024] In particular, at least one housing inner chamber may be provided
inside the ultrasonic transducer. This housing inner chamber may be at
least partially delimited by the second housing part, for example. This
housing inner chamber may be at least partially filled with a filler
and/or damping material in particular, for example, a damping molding
compound. Silicone is advisable for this purpose, for example.

[0025] The damping material may in particular be directly connected to the
transducer core, for example, the electroacoustic transducer element, and
may be configured to provide the most rapid possible damping after an
excitation of the transducer core. Furthermore, the filler and/or damping
material may be configured to dissipate pressure forces exerted by the
fluid medium on the transducer via the transducer core and the filler
and/or damping material on the rear side onto the second housing part.

[0026] In addition to the ultrasonic transducer in one or multiple of the
above-described embodiments, a method for manufacturing an ultrasonic
transducer for use in a fluid medium is also proposed. The method may be
used in particular for manufacturing an ultrasonic transducer in one or
multiple of the above-described embodiments; however, other types of
ultrasonic transducers are also fundamentally manufacturable with the aid
of the proposed method. The method includes the steps described
hereafter, which do not necessarily have to be carried out in the
described sequence. Individual method steps may also be carried out
simultaneously and/or overlapping in time. Furthermore, individual or
multiple method steps may be carried out repeatedly.

[0027] In the method, a transducer core is produced, which includes at
least one electroacoustic transducer element. Furthermore, in another
method step, at least one first housing part is provided in such a way
that the first housing part at least partially encloses the transducer
core. At this point in time, the transducer core may already be
completely implemented; however, it may also be implemented only
partially, for example, in that at this point in time only an adjusting
body of the transducer core is provided, which is at least partially
enclosed by the first housing part. The first housing part is implemented
in such a way and is provided in such a way that a rear side of the
electroacoustic transducer element, which faces away from the fluid
medium, is accessible, for example, for an electrical contacting process.
In another method step, at least one second housing part is provided.
This second housing part is connected to the first housing part in such a
way that the ultrasonic transducer is essentially terminated on its side,
which faces away from the fluid medium, by the second housing part.

[0028] The manufacturing method may be designed particularly simply in
such a way that at least one sealing film, for example, of the
above-described type, is used. For example, this may be a plastic film,
for example, as explained in greater detail below, a polyimide film or
another film material. However, metallic films are also fundamentally
possible. The method may be implemented in such a way that the first
housing part and the transducer core or a part of the transducer core,
for example an adjusting body, are applied to the sealing film. In
particular, they may be connected to the sealing film, for example, by a
gluing process and/or another type of integral connection process. An
intermediate space between the transducer core or the part of the
transducer core and the first housing part is at least partially filled
up by at least one damping and/or decoupling material. For example, this
damping and/or decoupling material may include a plastic material, in
particular a liquid silicone rubber (LSR). The filling up may take place
with the aid of a molding process in particular.

[0029] Prior to connecting the first housing part and the second housing
part, a contact bridge for contacting the electroacoustic transducer
element may be connected to the first housing part in particular. This
connection may include a form-locked and/or force-fitted connection in
particular, as already explained above. The contact bridge may have
multiple coherent electrical contacts in particular, the electrical
contacts being able to be disconnected from one another after connecting
of the contact bridge to the first housing part, for example, after
applying of the second housing part to the first housing part.

[0030] The proposed ultrasonic transducer and the proposed method have
numerous advantages over known ultrasonic transducers and known
manufacturing methods. Thus, a foundation is formed for a cost-effective
ultrasonic transducer, which is manufacturable in mass production, for
example, an air ultrasonic transducer, as may be used for gas flow
measurement in the automotive field, for example. An ultrasonic
transducer may be used as an ultrasonic flow meter on the pressure side
of turbocharged internal combustion engines, for example.

[0031] The ultrasonic transducer may be constructed simply and
cost-effectively. Thus, the ultrasonic transducer may be manufactured on
the basis of a piezoceramic, optionally having an impedance adjustment
layer, having a housing in the form of a two-part sleeve, for example.
The first housing part may be implemented as the front-side part of the
sleeve and may be connected to the adjustment layer. This connection may
occur via at least one decoupling element and/or at least one sealing
film and/or a coating and/or a combination of these elements, for
example. The first housing part, for example the front-side part of the
entire sleeve, may be implemented as flat in such a way that the rear
side of the piezo is located approximately in one plane together with the
rear sleeve edge. The piezo may accordingly be well accessible during the
installation, gluing, and contacting processes. The second housing part
may in particular be implemented as the rear-side sleeve part. This
second housing part may be implemented as a deeper sleeve part than the
first housing part. The second housing part may accordingly accommodate a
damping and/or a decoupling and/or a supporting material as described
above, for example a molding material.

[0032] Good accessibility to the piezo rear side is ensured by the at
least two-part embodiment of the housing, for example, with the aid of
the embodiment of the two-part sleeve, preferably having a relatively
flat front part. An advantageous manufacturing sequence may be
implemented in this way. The present invention allows more degrees of
freedom of the design as a whole, for example, with respect to the
selection of the contacting technology. Finally, special requirements for
the ultrasonic transducer may be met in this way, for example,
requirements of the automotive field, in particular engine attachment
conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows a sectional view of an exemplary embodiment of an
ultrasonic transducer according to the present invention.

[0034] FIG. 2 shows a sectional view of the exemplary embodiment in FIG. 1
having its sectional plane perpendicular to the section plane in FIG. 1.

[0035] FIG. 3 shows an exemplary embodiment of a contact bridge.

DETAILED DESCRIPTION OF THE INVENTION

[0036] One possible exemplary embodiment of an ultrasonic transducer 110
according to the present invention is shown in FIGS. 1 and 2. FIG. 1
shows a sectional view from the side, while in contrast FIG. 2 shows a
sectional view perpendicular to the sectional plane in FIG. 1 in the top
view. Ultrasonic transducer 110 includes a transducer core 112, which in
turn includes an electroacoustic transducer element 114 and an adjusting
body 116. Adjusting body 116 may be implemented, for example, as a
λ/4 impedance adjustment layer. Electroacoustic transducer element
114 may be implemented, for example, as a piezoelement and may be
connected directly or via at least one intermediate layer (for example,
an intermediate layer to compensate for thermomechanical tensions) to
adjusting body 116. In the illustrated exemplary embodiment, adjusting
body 116 has a slightly greater diameter d1 than electroacoustic
transducer element 114. For example, entire transducer core 112 may
therefore have diameter d1 as a whole, for example, a diameter of 8
mm.

[0037] Transducer core 112 is introduced into a housing 118, which is
implemented in two parts in the illustrated exemplary embodiment. More
than two parts may also fundamentally be provided. Housing 118
accordingly includes a front-side housing part 122, which faces toward a
fluid medium 120 (see FIG. 1) in use, and a rear-side second housing part
124, which faces away from fluid medium 120. First housing part 122,
which is also referred to hereafter as the first housing sleeve or the
front-side sleeve, may be implemented as an essentially
cylinder-symmetrical sleeve, for example. As an example, in the
illustrated exemplary embodiment, first housing part 122 has an angular
design in a section view and has an axial part 128 extending in parallel
to an axis 126 and a radial part 130 extending essentially
perpendicularly to axis 126. Radial part 130 has a front surface 132,
which faces toward fluid medium 120. This front surface 132 is
implemented in the form of a circular ring, for example. It has an
internal diameter d2 of 12 mm, for example. Accordingly, an
intermediate space 134 may be designed between transducer core 112 and
first housing part 122, which at least partially surrounds the transducer
core. This intermediate space 134 may be implemented in the present case
essentially in the form of a cylindrical sleeve, for example, having a
thickness of 1 mm, for example. Intermediate space 134 may be entirely or
partially filled up using a decoupling element 136, for example, as shown
in the exemplary embodiment in FIGS. 1 and 2, which does ensure good
mechanical fixation of transducer core 112 in housing 118, but at least
partially damps a structure-borne noise transmission between housing 118
and transducer core 112. For example, a molding material may be used as
the material for decoupling element 136, for example a liquid silicone
rubber (LSR).

[0038] Transducer core 112 has an emission surface 138 on its side, which
faces toward fluid medium 120. In the illustrated exemplary embodiment,
this emission surface is situated in one plane together with front
surface 132 of first housing part 122. The side of decoupling element
136, which faces toward fluid medium 120, preferably also does not
protrude beyond this common plane of surfaces 132 and 138. Ultrasonic
transducer 110 may be sealed to fluid medium 120 via at least one sealing
element 140, for example a sealing film 142. Alternatively or
additionally, other types of sealing elements 140 also come into
consideration, for example coatings. The sealing film may, for example,
be connected over a large area to emission surface 138 and/or front
surface 132, for example, by gluing.

[0039] On the rear side, i.e., on the side which faces away from fluid
medium 120, first housing part 122 is implemented as comparatively short,
so that in the illustrated exemplary embodiment, the rear side of
transducer core 112 is aligned flush with the rear side of first housing
part 122 or even protrudes beyond it. Electroacoustic transducer element
114 is accordingly preferably freely accessible from the rear side.

[0040] Electroacoustic transducer element 114 is contacted via a contact
bridge 144. This contact bridge 144 is guided, for example, in a radial
expansion 146 of second housing part 124, which is otherwise implemented
as essentially cylindrical, for example as pot-shaped. Contact bridge 144
is guided outward at its upper end through an opening 150 in second
housing part 124 and preferably has connecting elements 148 on its lower
end for connecting to first housing part 122. These connection elements
148 are implemented in the form of clips or hooks in the illustrated
exemplary embodiment, as is apparent from FIG. 1, for example, and may be
put and/or clamped over the rear end of axial part 128 of first housing
part 122. A form-locked and/or force-fitted connection may, for example,
be achieved in this way.

[0041] Contact bridge 144 is shown as an example in FIG. 3. It is
accordingly apparent that contact bridge 144 has two electrical contacts
152, 154 in the illustrated exemplary embodiment, which may be connected
to one another at their upper end by a web 156, for example. This web 156
may be removed after assembly of ultrasonic transducer 110, as explained
in greater detail below. Connection elements 148 may protrude laterally,
for example, by 2.2 mm, beyond electrical contacts 152, 154, which extend
essentially axially. Electrical contacts 152, 154 may also have a width
of 2.2 mm, for example, and may be spaced apart by 1.4 mm, for example.
Electrical contacts 152, 154 may provide contacting surfaces 158, as is
apparent from FIG. 1, for example. A contacting 160 to corresponding
contacts of electroacoustic transducer element 114 may be guided via
these contacting surfaces 158, for example, by wire bonding, for example.
Since the rear side of transducer core 112 is also comparatively freely
accessible when transducer core 112 is introduced into first housing part
122 and before second housing part 124 is applied, such contacting is
also easily possible by application of wires, for example, or with the
aid of other bonding technologies or clamping technologies or other
contacting technologies.

[0042] After this contacting, second housing part 124, which is
pot-shaped, for example, is applied to first housing part 122 and
connected thereto, for example by ultrasonic welding. The connection is
identified by reference numeral 162 in FIG. 1. An inner chamber 164 is
thus formed on the side of transducer core 112, which faces away from
fluid medium 120. This inner chamber 164 may be implemented as
voluminous, for example, so that it may be completely or partially filled
up using at least one filler and/or damping material 166, for example, a
damping molding compound, for example. For this purpose, first housing
part 122 may include one or multiple openings 168, for example, which may
subsequently be closed off or which may also remain in housing 118.

[0043] In the illustrated exemplary embodiment according to FIGS. 1 and 2,
ultrasonic transducer 110 is thus implemented having a two-part housing
118, for example, a two-part sleeve. A transducer front points downward,
toward fluid medium 120 in FIG. 1. A corresponding front-side sleeve part
may be implemented as ring-shaped, for example. To manufacture ultrasonic
transducer 110 according to FIGS. 1 and 2, front surface 132 of first
housing part 122 may be glued onto sealing film 142, for example.
Adjusting body 116 may also be glued onto this sealing film 142, so that
these elements are fixed. For example, polyimide film (for example,
Kapton) may be used as sealing film 142. Decoupling element 136 may be
injected and/or embedded in an injection mold as the acoustic decoupling,
for example, an LSR material. Electroacoustic transducer element 114 may
subsequently be glued on, and connection elements 148, for example the
contact pins, of contact bridge 144 may be clipped on axial part 128. As
shown in FIGS. 1 and 2, a coherent contact bridge 144 may be used.
However, individual contact pins may also alternatively or additionally
be used. For example, contact bridge 144 may be opened after the assembly
of ultrasonic transducer 110. Contacting 160 may subsequently be applied.
For example, copper wires or strips may be fastened via
thermo-compression welding on the piezoelectrodes and/or contacting
surfaces 158, for example the contact lands of the contact pins, for
example of contact bridge 144. Alternatively, at least a part of contact
bridge 144 may be fastened directly, for example by welding, on the
piezoelectrodes and/or contacting surfaces 158. The rear-side sleeve part
in the form of second housing part 124 may subsequently be put on and may
be connected to first housing part 122, for example the sleeve ring, in
particular by ultrasonic welding. A damping molding compound and/or
another filler or damping material 166 may subsequently be filled in and
cured. Rear-side opening 168 may be used not only for filling in filler
or damping material 166, but rather may also allow a compensation for
thermal expansions of the damping molding compound within the sensor
operating range. On the other hand, this opening 168 is only to be
dimensioned as sufficiently large that the transducer interior, i.e.,
inner chamber 164, may still be sufficiently supported to the rear on the
sleeve in the event of counter pressure of fluid medium 120 to be
measured, for example, air. The size of opening 168 and/or its geometric
embodiment may be implemented for this purpose as a function of the
filling volume or the filling geometry and the hardness and the
coefficients of expansion of the participating materials in such a way
that the emission surface, which faces toward the fluid medium, moves as
little as possible both in the event of compression load and also in the
event of thermal load.

[0044] Ultrasonic transducer 110 shown in FIGS. 1 and 2 only shows one of
multiple exemplary embodiments. The exemplary embodiment, and also other
exemplary embodiments of the present invention, may be advantageously
refined and/or altered in various ways. Thus, for example, an internal
decoupling may be provided, which offers a well-defined, hard, and easily
sealable mechanical interface to the outside. The material of housing 118
may preferably be manufactured from plastic, since plastic has a
particularly good decoupling property. Structure-borne noise components,
which are transmitted, for example, via damping material 166, decoupling
element 136, or sealing film 142, for example, are sufficiently damped
because of the sound damping of the plastic. A liquid crystal polymer
(LCP) is particularly suitable, since it is particularly suitable for
manufacturing filigree structures and it simultaneously has good
intrinsic damping. Other materials are, for example, PPA, PBT, PEEK, or
other plastics. The plastic materials may be used in filled or unfilled
form, for example, having a filler made of glass fibers, ceramic, carbon,
or similar materials. Furthermore, metal and/or a composite material may
alternatively or additionally be selected as the material for housing 118
and/or housing parts 122, 124. For example, metal as the sleeve material
and/or metal parts inlaid in plastic allow EMC shielding. However, metal
tends to have rather long-lasting natural vibrations, which could impair
the decoupling properties. In the case of plastic as the sleeve material
or as the material of housing 118, contact bridge 144 may also be divided
into three instead of only two segments or electrical contacts 152, for
example, of which two segments are used for the piezocontacting, for
example, and the third segment may represent a shield in the form of a
ring or partial ring for electroacoustic transducer element 114 and/or
other parts of ultrasonic transducer 110.

[0045] As described above, polyimide (for example, Kapton) may come into
consideration as the material for sealing film 142, for example. Other
alternatively or additionally usable materials are, for example,
fluorinated hydrocarbons, such as Teflon and/or PEEK, other types of
thermoplastic or duroplastic materials, or also coatings which are not
applied as a film, for example, parylenes, lacquers, or similar
materials.

[0046] Alternatively or additionally to the planar gluing of sealing film
142 to first housing part 122, other connection technologies also come
into consideration. Furthermore, the film edge of sealing film 142 may
also still be sealed separately. This may be performed simultaneously
with the gluing of ultrasonic transducer 110 in a higher-level sensor
housing, for example, which is not shown in the figures. For example,
multiple such ultrasonic transducers 110 may also be situated in such a
higher-order sensor housing, as is shown in the above-cited related art
and/or in published German patent application document DE 10 2004 061404
A1. The sensor systems described therein may also be implemented using an
ultrasonic transducer 110 according to the present invention.

[0047] Sealing film 142 may be glued onto the sleeve ring of first housing
part 122 and onto adjusting body 116 in a separate processing step.
However, a connection between sealing film 142 and first housing part 122
and/or adjusting body 116 may also additionally or alternatively be
produced in another way, for example, in a step including the
introduction of decoupling element 136, for example in an injection mold,
for example an LSR mold. Alternatively or additionally, the connection
may also be performed shortly before or after the LSR process and/or
another injection-molding process for introducing decoupling element 136,
for example, by the same contact pressure which also closes or seals the
mold, for example the LSR mold.

[0048] Alternatively or additionally, other types of decoupling elements
136 may also be used. Decoupling element 136 may thus also be implemented
and/or installed entirely or partially as a molded part. One advantage of
this procedure could be a lower strain on the adjustment layer material.
However, a fundamentally higher tolerance because of the softer
consistency is disadvantageous in this case. Another variant, which may
be used alternatively or additionally, is extrusion coating of the
material of decoupling element 136, for example the LSR, only on first
housing part 122 and optionally sealing film 142, while adjusting body
116 is applied, for example glued on, in a separate processing step.

[0049] Alternatively to the LSR process, a damping and/or decoupling
material may also be introduced with the aid of a casting technology.
Other materials may also be used instead of silicone. Decoupling element
136 may also be omitted as a separate material and/or may be entirely or
partially combined with damping material 166. For example, a single
molding material may be used, which represents a compromise between
damping and decoupling. This may be a silicone material, for example.
Flexibilized epoxides having additional fillers are also conceivable as
the basic material, for example.

[0050] Further modifications and/or refinements relate to adjusting body
116. For example, it may be implemented according to the above-described
related art. In particular, adjusting body 116 may be made of epoxide,
filled with hollow glass beads, and/or porous sintered polyimide, for
example, polyimide of the type Vespel from DuPont or other materials
and/or also gradient materials, whose acoustic impedance or whose
impedance curve is selected in such a way that a favorable coupling is
provided between electroacoustic transducer element 114 and fluid element
120. One or multiple additional layers may be placed between
electroacoustic transducer element 114 and adjusting body 116, which
protect electroacoustic transducer element 114, for example the piezo,
from pretensions in that they have coefficients of expansion close to the
piezomaterial, for example (i.e., in the magnitude of 10 ppm/K or less,
for example), and have a sufficient thickness. This at least one layer
may simultaneously be used for the purpose of sealing open pores of
adjusting body 116 against an adhesive, using which electroacoustic
transducer element 114 is fastened. This at least one optional additional
layer may be glued or applied by a molding method, for example, and/or
may be part of adjusting body 116, for example the adjustment layer, in
particular having different thermal/acoustic properties.

[0051] The diameter of electroacoustic transducer element 114 may be
selected in such a way that essentially the planar resonance is exploited
for the ultrasound generation and/or ultrasound detection. The thickness
of electroacoustic transducer element 114 may represent a compromise. The
thinner the piezo is selected, for example, the more flexible it is,
which makes it more stable with respect to thermal shocks. On the other
hand, an excessively thin piezo executes excessively strong bending
oscillations, which may result together with adjusting body 116 in an
excessively strong temperature sensitivity of ultrasonic transducer 110.
The connection between electroacoustic transducer element 114 and
adjusting body 116 or a compensation layer may also be performed without
a separate adhesive, for example, in that a piezoelement is embedded
directly into adjusting body 116 and/or at least one intermediate body.
The connection between electroacoustic transducer element 114 and
adjusting body 116 and/or the optional compensation layer may be
flexibilized so that the piezofunction is not impaired by the thermal
change of adjusting body 116 or the compensation layer or by temperature
shock. On the other hand, the connection is preferably selected as
sufficiently hard that a sufficient acoustic coupling is present. An
epoxy-based material may typically be used for this purpose.

[0052] The electrical connection between the electrodes of electroacoustic
transducer element 114, for example, the piezo, and the contact bridge,
which may generally comprise one or multiple contact pins, may be
produced in various ways. For example, as explained above, a connection
may be performed using wires, strips, films, or also litz wires. Instead
of the mentioned thermo-compression welding, other technologies also
fundamentally come into consideration as the contacting. For example,
conductive adhesives, solders, or wire bonds suggest themselves. The
contact points or also the entire connection between the electroacoustic
transducer element and contact bridge 144 and/or individual contact pins
of this contact bridge 144 may be covered using a hard protective
compound, for example a glob top compound and/or using soft silicone gel,
in order to protect them, for example from corrosion. The contact pins
may fundamentally also be fixedly connected to one of the housing parts
of housing 118, for example, as an inlet part or as a lead frame and/or
as extrusion-coated parts.